1. Field of the Invention
This invention relates in general to surface condition sensing systems, and, more particularly, to ice and water detection systems for roadways and ice detection systems for aerodynamic structures of aircraft.
2. Description of the Related Art
Ice and water build-up on surfaces can pose deadly problems for certain kinds of transport.
Wet or icy roads can be extremely hazardous for vehicle drivers. For instance, in 1981, authorities in the United Kingdom reported that approximately one third of all vehicle collisions took place on wet roads. Studies on traction indicate that the presence of ice can significantly reduce traction. Because current traction control algorithms are optimized for one surface situation only (for example, dry roads), current antilock braking systems (ABS) are only 50% efficient on ice compared to their operation on a dry roadway. If traction control and ABS systems could be informed about the presence of water or ice on the roadway, vehicle safety could be significantly improved. Also, fixed ice detection systems mounted above or within bridges or other ice-prone areas could alert approaching drivers as to the presence of hazardous ice or water.
Likewise, icing, or ice layer build-up on aircraft wings, is a major concern of pilots flying not only in the winter months, but also at high altitudes where the moisture and constant cold temperature can cause ice to form in an otherwise cloudless sky. Once ice layers form on aircraft wings, the ice layers disturb the laminar flow over the wing, resulting in a loss of lift and the creation of dangerous flying conditions. Many air crashes have been traced to undetected icing on the wings.
Previous road or aircraft wing condition sensing systems were generally static in nature and required the temperature of the road bed or visually observed wing surface in order to make a decision about the presence of ice. A thermocouple or other means had to be placed on or in the road or surface in order to provide the needed temperature information.
The present invention, in contradistinction, infers the presence of ice from microwave signatures alone, making the invention completely contactless and capable of being carried by a vehicle to perform real time sensing of the road condition on which the vehicle is moving, or to constantly monitor for ice build-up on an aircraft in flight or on the ground.
Also, previous devices using a single microwave frequency to find water depth on a road surface have been limited to monitoring thin layers of ice or have required the associated measurement of road temperature and atmospheric humidity to infer the presence of ice. Another one of the innovative aspects of the present invention is the reliable detection of ice or water layers on a surface through processing of reflectance as a function of a range of microwave frequencies without the need for concurrent measurement of the surface temperature.